This disclosure relates to hydraulic devices of the expanding, contracting-chamber type and particularly to hydraulic devices in which the chambers are formed by a gerotor gearset.
Typically, such hydraulic devices have utility as both motors and as pumping devices and conventionally include commutation-valve arrangements for directing fluid to and from the chambers from one axial side of the gerotor gearset. Illustrative of such a hydraulic device is U.S. Pat. No. 3,452,680, patented July 1, 1969, and assigned to the assignee of the present invention. The commutation-valve arrangements which are generally used with such devices often include a fairly complex series of fluid channels, and in order to properly distribute and remove the fluid in proper sequence from the chambers, some of the channels are necessarily of fairly small dimension. Therefore, it has been found that such hydraulic devices, particularly when employed as pumping units, are at times subject to operating at less than full volumetric efficiency when the fluid, due to the complex path it follows through the commutation-valve arrangement, is insufficient to fully fill the chambers during their expansion cycles.